The same appendix gives more information on the Shire Calendar's background in the fictional history of Middle-earth, stating that the Shire Reckoning is a conservative continuation of the calendar of Númenor as used in Middle-earth during the Second Age, but revised in the Third Age by Mardil and Hador, the first and seventh ruling Stewards of Gondor.
The Hobbits retained the unreformed King's Reckoning, but introduced a reform that resulted in a fixed number of weeks (in imitation of the historical 10th-century Icelandic calendar).

Appendix D further gives some information on the Reckoning of Rivendell, the calendar used by the Elves in Imladris (Rivendell), which divided the solar year into six "seasons" or "long months".

The only allusion to a calendar of the Dwarves is made in The Hobbit, regarding the "dwarves' New Year" or Durin's Day.

Tolkien repeatedly stresses that his legendarium is set in a remote past of our Earth (as opposed to a completely fictional or mythological world),[1] and he gives intercalation methods used by the Númenoreans that amount to an average length of a year of 365.24 days and an average year in the 'Reckoning of Rivendell' of ​52595⁄144≈365.24306 days.
With the caveat "if the year was then of the same length as now" Tolkien goes on to discuss historical intercalation
made by the Númenoreans and their descendants, the Dúnedain, during the Second and Third Ages, assuming a tropical year of 365.2422 days.[2]

The seasons referred to in Tolkien's calendars, and in his writings in general, are those of the Northern Hemisphere.

Contents

The Shire calendar or Shire Reckoning is used by the Hobbits of the Shire. Tolkien based it on the calendar reported by Bede.

The Middle-earth roots of the Shire calendar lie in Rhovanion hundreds of years before the Shire is founded. There the ancestors of Hobbits acquire a system of months (and their names) from the Men of that region.

When Hobbits migrate into Eriador, they take up the Kings' Reckoning, but maintain their old names of the months. In the King's Reckoning, the year begins on the winter solstice.

After migrating further to the Shire, its Hobbits begin Shire Reckoning, a new system of numbering the year. Year 1 of Shire Reckoning corresponds to the foundation of the Shire in the year 1601 of the Third Age (the founders are the Bree Hobbits Marcho and Blanco). Therefore, years of the Third Age can be converted to Shire-years by subtracting 1600. The last year of the Third Age is year 1421 on the Shire calendar. A year in the Shire is the same length as our year – 365 days, 5 hours, 48 minutes, 46 seconds. The Shire's calendar year is also divided into 12 months but all of 30 days. Five additional days are added to create a 365-day year.

For the names of the months, Tolkien used reconstructed names derived from the Anglo-Saxons; in other words, they are Tolkien's take on what English would be actually using now if it had not adopted Latin names for the months (January, February, March, etc.).

The Yuledays are the days that signify the end of an old year and the beginning of a new one, so 2 Yule is the first day of the year. The Lithedays are the three days in the middle of the year, 1 Lithe, Mid-year's Day, and 2 Lithe. In leap years (every fourth year except centennial years) a day is added after Mid-year's Day called Overlithe. All these days are placed outside of any month. These days are primarily holidays and feast days. Mid-year's Day is meant to correspond to the summer solstice, which Tolkien describes as being 10 days earlier than the middle day of our year. However, since then the summer solstice has shifted slightly so it falls on a different date now, rendering the difference between Mid-year's Day and the middle day of our year eleven days, instead of ten.

There are seven days in the Shire week. The first day of the week is called Sterday and the last day of the week is called Highday. The Mid-year's Day and, when present, Overlithe have no weekday assignments. This arrangement is used because it causes every day to have the same weekday designation from year to year (instead of changing as in the Gregorian calendar).[3]

Highday is a holiday with evening feasts. Tolkien states that Highday is more equivalent to our Sunday, and so translated the terms "Mersday" and "Highday" used in one of Bilbo's songs as "Saturday" and "Sunday" rather than "Thursday" and "Friday".

In The Hobbit and The Lord of the Rings, the names of months and days are given in modern equivalents. For instance, Afteryule is called January and Sterday is called Saturday.

Lithe is a Midsummer holiday in the Shire. It is mentioned in The Fellowship of the Ring. Lithe falls between Forelithe, the sixth month of the year, and Afterlithe, the seventh month. In most years there are three Lithedays: 1 Lithe, Midyear's Day, and 2 Lithe. In Leap-years there is a fourth Litheday called Overlithe between Midyear's Day and 2 Lithe. Midyear's Day and Overlithe are not assigned any weekday, while 1 Lithe always falls on a Friday and 2 Lithe is a Saturday. Lithe and the Midwinter holiday called Yule are the two major holidays in the Shire. Lithe is a time of great feasting and merriment. During Lithe, the Free Fair is held on the White Downs, where Hobbits gather to celebrate and to buy and sell goods. Every seven years at the Free Fair during Lithe, an election is held for the office of Mayor of the Shire. In the years that Overlithe occur, it is a day of special celebration. Overlithe falls during the Great Year of Plenty in 3020 after the War of the Ring, and it is the merriest holiday in the history of the Shire.

The word lithe is from the Old English líða. This may have been the name for Midsummer, while ærra Líða and æftera Líða were used for the months June and July. The word lithe means "mild, balmy" in relation to the weather.

The Hobbits, who have adopted the King's Reckoning, alter it in a different way from the Steward's Reckoning. Like the Steward's Reckoning, they have twelve months of thirty days, and five holidays outside the months. However, they have three "extra" days in midsummer and two in midwinter, similar to the Elven calendar. In the Shire the three days of midsummer are called Lithedays, and the two days of midwinter are the Yuledays. In leap years, the extra day is added to the Lithedays and called Overlithe. The other innovation in the Shire calendar is to make Midsummer's Day (and the Overlithe) outside the week, as well as the month, meaning the days of the week will not change in relation to the days of the year. The Shire Reckoning is the calendar used in the Red Book of Westmarch, and hence in The Lord of the Rings. It counts from the founding of the Shire in T.A. 1600.

The Hobbit names of the months come from names used in the vales of Anduin in antiquity, and their meanings are often obscure or forgotten. They are:

Shire name

Bree name

2 Yule

2 Yule

Afteryule

Frery

Solmath

Solmath

Rethe

Rethe

Astron

Chithing

Thrimidge

Thrimidge

Forelithe

Lithe

1 Lithe

First Summerday

Midyear's Day

Second Summerday

Overlithe

Third Summerday

2 Lithe

Third/Fourth Summerday

Afterlithe

Mede

Wedmath

Wedmath

Halimath

Harvestmath

Winterfilth

Wintring

Blotmath

Blooting

Foreyule

Yulemath

1 Yule

1 Yule

(Given the decidedly Old English sound of these names, it can be assumed that this is Tolkien's "translation" of the archaic Westron.)

Overlithe occurs only in leap years. 2 Yule corresponds with December 22.

Although Yule is celebrated in the midwinter in the Shire, it is in some ways different from the more recently historical Yule practices in England.

The Shire's fictional Yule consists of two days called 1 Yule and 2 Yule. The last day of the year is 1 Yule and the first day of the next year is 2 Yule. The Yuledays fall between the months called Foreyule and Afteryule and are not part of either month. 1 Yule is always on a Friday and 2 Yule falls on Saturday.

Yule is one of the two chief holidays in the Shire—the other being the midsummer holiday called Lithe. The Yule celebrations last six days in total, including two days before and two days after the Yuledays. This six-day period is called Yuletide. It is a time of feasting and merriment.

After the War of the Ring, it is feared that the Yule feasts will be rather meagre due to shortages of provisions in the Shire. But large stores of food and beer are found in the tunnels of Michel Delving and in the quarries at Scary and in other places, so the Yuledays are a time of great cheer.

The Elves do not have a celebration at midwinter. It appears that the Rohirrim maintain the custom of celebrating the midwinter holiday as their ancestors the Northmen had done. The name of the holiday in Rohan is not known but it was most likely similar to "Yule."

"the Quenya word yén, often translated "year", really means 144 of our years. The Eldar preferred to reckon in sixes and twelves as far as possible. A 'day' of the sun they called ré and reckoned from sunset to sunset. The yén contained 52,596 days. For ritual rather than practical purposes the Eldar observed a week or enquië of six days; and the yén contained 8,766 of these enquiër"

The Elves also have a regular 365-day solar year called coranar meaning "sun-round" or more commonly loa meaning "growth".
The Elven year, which began near the northward equinox, is divided into six seasons or 'months' which consist of four 54-day months and two 72-day months.
Five or eight extra days outside the seasons make the length of the loa 365 or 368 days. Most years are 365 days, but every twelfth year is 368 days, resulting in an average year of 365.25 days with the additional suggestion that the 'Reckoning of Rivendell'
made a further correction by omitting the three extra days in every third yén (once every 432 years), for an average year length of ​52595⁄144≈365.24306 days.[5]

Five other days, two between coirë and tuilë and three between yávië and quellë, meant the calendar added up to 365 days. Irregularities were allowed for by adding another three days every twelve years, except the last year of a yén.

The calendar developed by the Men of Middle-earth is called the King's Reckoning, and is in many ways similar to our own (Gregorian). It has a week of seven days. The calendar year has 365 days (except in leap-years), and twelve months (astar): ten with 30 days and two with 31.

Unlike the Gregorian calendar, the King's Reckoning has some days outside the months. These special monthless days, a feature borrowed from Elvish Calendars, were generally holidays. Two of these special days were the pair which book-ends the year; thus, in the King's Reckoning, the last month of the year is followed by mettarë, the last day of the year; this is then followed yestarë, New Year's Day, which is not however part of the first month. The other monthless day is loëndë, mid-year day. In a leap year there two mid-year days.

Various irregularities occur in this calendar, especially following the Downfall. In T.A. 2060, Mardil Voronwë revises the calendar, and the new version becomes the Steward's Reckoning. The months of Steward's Reckoning all have 30 days, and there are two additional "extra" days at the equinoxes, tuilérë and yáviérë. The five extra days (the equinoxes, midsummer and two at midwinter) are holidays.

In T.A. 3019, the Reunited Kingdom adopts a New Reckoning, which begins the year on March 25 (Lady Day, the English new year between 1155 and 1752), the date of the downfall of Sauron. This makes it correspond more closely to the spring beginning of the Elven calendar.

The months of the Reckonings are in Quenya (or Sindarin among the Dúnedain) and are:

According to Jim Allan in An Introduction to Elvish, the Númenórean Calendar is similar to the French Republican Calendar. For example, the names of the third month of Winter, Súlímë and Ventôse, both mean 'Windy'. When lined up in this way, most of the month names have matching or similar meanings.[8]

"The first day of the dwarves' New Year [...] is as all should know the first day of the last moon of Autumn on the threshold of Winter."

In The Hobbit, the secret writing on the map that Gandalf had received from Thráin II mentioned Durin's Day. It predicted that on Durin's Day the last light of the Sun as night fell would reveal the secret door into the Lonely Mountain. This came true later that year (T.A. 2941), when the new moon appeared a week before the end of autumn.

Astronomer Bradley E. Schaefer has analysed the astronomical determinants of Durin's Day. He concluded that, as with all real-world lunar calendars, the date of Durin's Day is observational, dependent on the visibility of the first waxing crescent moon.[13]

^"the year no doubt was of the same length [as ours], for long ago as those times are now reckoned in years and lives of men, they were not very remote according to the memory of the Earth" Appendix D.

^This was the value cited in textbooks in the 1940s, e.g. William Marshall Smart, Text-book on Spherical Astronomy Author, 1947, p. 141.

^"How any resulting inaccuracy was dealt with is uncertain. If the year was then of the same length as now, the yén would have been more than a day too long. That there was an inaccuracy is shown by a not in the Calendars of the Red Book to the effect that in the 'Reckoning of Rivendell' the last year of every third yén was shortened by three days: the doubling of the three enderi due in that year was omitted; 'but that has not happened in our time'."